To be in

to be at home; as, Mrs. A. is in.
- Knight.

See also: In

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in classic literature ?
Irwine, with whom I desire you to be in perfect charity, far as he may be from satisfying your demands on the clerical character.
Even these men seemed to be in darkness too; for no light shone through the chinks in the door, nor were they moving, as their custom was, but quite still: the silence being unbroken by so much as the creaking of a board.
"Consumers in the future are going to be in vehicles, highly technologically driven, electrically powered, and they probably won't own the vehicles.